J. Christensen-Dalsgaard, W. Däppen, S. V. Ajukov, E. R. Anderson, H. M. Antia, S. Basu, V. A. Baturin, G. Berthomieu, B. Chaboyer, S. M. Chitre, A. N. Cox, P. Demarque, J. Donatowicz, W. A. Dziembowski, M. Gabriel, D. O. Gough, D. B. Guenther, J. A. Guzik, J. W. Harvey, F. Hill, G. Houdek, C. A. Iglesias, A. G. Kosovichev, J. W. Leibacher, P. Morel, C. R. Proffitt, J. Provost, J. Reiter, E. J. Rhodes Jr., F. J. Rogers, I. W. Roxburgh, M. J. Thompson, R. K. Ulrich

Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations.

J. Christensen-Dalsgaard and S. Basu are with Theoretical Astrophysics Center and Institute of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark. W. Däppen and E. J. Rhodes Jr. are with the Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA. S. V. Ajukov is with the Sternberg Astronomical Institute, Moscow, Russia. E. R. Anderson, J. W. Harvey, F. Hill, and J. W. Leibacher are with the National Solar Observatory, National Optical Astronomy Observatories, Tucson, AZ 85726, USA. H. M. Antia and S. M. Chitre are with the Tata Institute of Fundamental Research, Bombay, India. V. A. Baturin, I. W. Roxburgh, and M. J. Thompson are with the Astronomy Unit, Queen Mary and Westfield College, London E1 4NS, UK. G. Berthomieu, P. Morel, and J. Provost are with the Observatoire de la Côte d'Azur, Nice, France. B. Chaboyer is with CITA, University of Toronto, Toronto, Canada. A. N. Cox and J. A. Guzik are with Los Alamos National Laboratory, Los Alamos, NM 87545, USA. P. Demarque is with the Department of Astronomy, Yale University, New Haven, CT 06520, USA. J. Donatowicz and G. Houdek are with the Institut für Astronomie, Universität Wien, Vienna, Austria. W. A. Dziembowski is with the Copernicus Center, Warsaw, Poland. M. Gabriel is with the Institut d'Astrophysique, Université de Liège, Liège, Belgium. D. O. Gough is with the Institute of Astronomy, University of Cambridge, Cambridge, UK. D. B. Guenther is with the Department of Astronomy and Physics, Saint Mary's University, Halifax, Nova Scotia, Canada. C. A. Iglesias and F. J. Rogers are with the Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. A. G. Kosovichev is with Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305, USA. C. R. Proffitt is with Computer Sciences Corporation, Goddard Space Flight Center, Greenbelt, MD 20771, USA. J. Reiter is with the Mathematisches Institut, Technische Universität München, Munich, Germany. R. K. Ulrich is with the Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA.